A series of large wildfires as seen heading east approaching Bastrop, Texas on Highway 71, Monday, Sep. 5. A roaring wildfire raced unchecked Monday through rain-starved farm and ranchland in Texas, destroying nearly 500 homes during a rapid advance fanned in part by howling winds from the remnants of tropical storm Lee.

Atlanta — Raging wildfires destroyed more than 1,000 homes in Texas over the weekend and thousands of residents were evacuated from the most-threatened areas. Ten new fires labeled "large" by the Texas Forest Service cropped up Monday night across the state.

Drought conditions, high winds, and large amounts of dry, combustible brush are ultimately to blame for some 21,000 wildfires that have hit the state since December.

The loss of homes in the rocky hill country highlights how the addition of 2 million residents every five years has pushed urban sprawl into wildfire danger zones, or as former Austin assistant fire chief Kevin Baum calls it, the "top of a matchstick."

Housing a booming population by pushing development outward is part of the reality of America's demographic ebb and flow from struggling states to booming ones, experts say. But this year's drought-driven wildfires have exposed the costs of strategies that put new homes in danger zones.

Some 5,000 people were evacuated ahead of the Bastrop County fire, which continued to burn unabated on Tuesday. By latest count, more than 600 homes have been destroyed there.

This weekend's fire damage is estimated to be $100 million, according to the Insurance Council of Texas.

A young woman and her 18-month-old daughter lost their lives near the Texas town of Gladewater, where a wildfire destroyed 20 homes over the weekend.

A total of 3.6 million square acres of Texas – approximately the size of Connecticut – have burned since December. Some of the most violent blazes of the year are currently burning in Hays, Travis, and Williamson counties, scorching some 40,000 acres so far.

"In rapidly growing population areas like Austin, as more and more of the desirable land fills up, you get kind of a pushing in and a pressure to build in the zone that everybody knows you shouldn't be building in," says George Rogers, a senior research fellow at Texas A&M University's Hazard Reduction and Recovery Center. "As your population expands, it's a natural consequence: You have built-in pressure to build in less safe places."

Twenty-five miles east of Austin, the state's second most popular destination for economic transplants from other states, Bastrop County is known as a film shoot location for Texas-flavored movies like "The Alamo" and as a redoubt of homes set on large, rural lots. Along with its central location, its idyllic setting has helped drive up the county's population by 30 percent in the past 10 years.

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The toll in Bastrop County is the largest such claim from a single fire in Texas history. Fanned by 40-mile-per-hour wind bands from tropical storm Lee, firefighters had to step aside and let the fires rage into residential areas. Firefighters on Tuesday are using the lull to try to get the upper hand on some 85 fires still burning throughout the state, with special emphasis on fires like the Bastrop County blaze lurking near populated areas.

The concerns aren't new: A 2003 FEMA study concluded that parts of Austin and its exurbs were ripe for the kinds of wildfires that have ravaged California in recent years, both for natural and man-made reasons: The placement of new homes on semi-arid ridges and flats brimming with dried-out plants and trees.

"Simply stated, the conditions ... as we find them today may be perfect for a natural wildfire disaster of significant (and prophetic) proportions," the 2003 report said.

Some of the most dire warnings raised in the report are now playing out across Texas.

"Keep in mind, there's of course nothing inherently dangerous about living in the country, but the danger comes under the right combination of conditions, raising the question, how can we, with any degree of confidence, forecast when we are in harm's way?" says Mr. Baum, a former Austin assistant fire chief who has studied the interface between urban sprawl and wildland vegetation.

"Right now, the weather is downright malevolent, like some kind of ugly, invisible hand that's preventing us from getting rain. That's created not just the perfect storm, but the perfect set-up for a situation like this where people have been caught offguard by the intensity and violence of these wildfires."